Tom Goskar's blog

Interactive Landscape Relighting

Imagine being able to view a whole landscape from any angle and from any height. Then imagine being able to move a virtual sun into any position, moving it at will to low grazing angles to enhance subtle features on the ground. We have discovered that a combination of Polynomial Texture Mapping, LiDAR, and 3D software enable us to do just that.

Polynomial Texture Mapping (PTM) is a technique which allows a photograph (normally of an object) to be interactively relit; the way it is illuminated is not fixed, and the viewer can change the lighting angle and intensity. PTM models are created by taking a series of photographs, each one illuminated from a different direction. Using software, the photos are then combined into a mathematical representation of the subject. Software viewers turn this data back into a photograph which you can light from any direction.

Surfaces and Light

I have worked with 3D surfaces in archaeology (including the 2002/3 Stonehenge laser scan project, and 3D visualisations of the Stonehenge World Heritage Site LiDAR) for some time, and know well how crucial light is to aid our perception of the detail on a surface. One of the first animations that I produced from the Stonehenge stone 53 scan data was of a light circling around the surface at a low angle to reveal the detail of the early Bronze Age carvings.

When I first was shown PTM in 2008, I quickly realised that we could use this technology to look at landscapes in the same way. Creating a ‘virtual PTM’ of objects and small amounts of topography from terrestrial laser scan data had already been done before but not, as far as I was aware, on a much larger scale. Would the technique scale up to an entire landscape?

Creating Virtual Polynomial Texture Maps

The images needed to create PTMs of smaller, real world objects are often captured using a hemispherical device called an illumination dome. This supports an array of photographic lamps. For my virtual PTM I would need a virtual illumination dome. Using 3D software, I constructed a regular dome of evenly spaced lights.

Given our previous work with 3D data of Stonehenge, and the surrounding World Heritage Site, it seemed like a good case study to continue with so Wessex Archaeology funded the development of the idea. Geoprocessing software was used to process the LiDAR tiles (kindly provided by the Environment Agency) into a very large Digital Elevation Model (DEM). This was ‘surfaced’ in our 3D software, turning millions of measurement points into an object on screen that looks solid.

Virtual illumination dome in software, with the solid model of the Stonehenge World Heritage Site

In my virtual environment, a camera was placed directly above the 3D landscape, at the top of the ‘dome’ facing down from a position that would, if in reality, be several kilometers in the air. After setting the ‘environment’ - that is how the lights affect objects and cast shadows, a digital image called a ‘render’ of the landscape was made for each lighting position. The result was a sequence of 62 images of the landscape, each illuminated from a different direction.

Below is a sample PTM of the land surrounding Stonehenge. It may take a minute to download on a fast connection. Click and drag your mouse around the image (which requires Java to be enabled on your computer) to move the light position. See how the Cursus and Avenue as well as field systems and barrows appear and disappear from view.

The processing power to produce a full 1:1 representation of the LiDAR data for the whole Stonehenge World Heritage Site is considerable and very time-consuming, but something which we hope to tackle. We will also publish more PTMs of other parts of the Stonehenge WHS and other LiDAR datasets as time allows, and post to this blog when we do so.

Wessex Archaeology now use this technique on our projects where appropriate. It is particularly well-suited for locating subtle surface features, and investigating anomalies identified using geophysics.

Find out more about Wessex Archaeology's Geomatics services, and other examples of archaeology and LiDAR.

Archaeocast 11 now online

The latest edition of our archaeology podcast, Archaeocast, is now online.
Listen to Archaeocast 11 to get a sense of what it is like to dive a shipwreck, including a live interview with one of our divers direct from the seabed. This edition of Archaeocast is presented by Gemma Ingason, outreach officer for our Heritage Lottery Funded coastal and marine archaeology programme, Time Travelling by Water.

Gemma Ingason interviews Graham Scott about his favourite shipwreck

Lasers and Light

Wessex Archaeology were asked to contribute an animation to the new touring version of last year's successful Making History exhibition, organised by the Society of Antiquaries of London. Over the next year, Making History will visit Salisbury, Stoke on Trent, Sunderland, and Lincoln. The exhibition will change at each venue to incorporate aspects of each region's own unique heritage.

Our animation, on show in Salisbury and South Wiltshire Museum until 3rd January 2009 (and at the end of this post!), gave us the opportunity to show some more of our work with the wonderful Stonehenge LiDAR dataset, as well as 3D laser scans of the Amesbury Archer's bones, and some new data captured with the University of Southampton's Archaeology department of WWI and WWII graffiti carved into trees on Salisbury Plain.


Lasers and Light from Wessex Archaeology on Vimeo.

LiDAR uses laser survey equipment mounted in an aeroplane to record the surface of the land below in three dimensions. The animation focuses on a field system in the Stonehenge World Heritage Site. Barely visible on the ground and in aerial photography, the features of the field system are revealed when a low level light is applied to the virtual landscape, throwing the virtual landscape into relief. The light source circles the earthworks, so their extent can be seen from all angles

Lasers can also be used on a smaller scale to study objects in greater detail. Here the skull and some of the long bones from the Amesbury Archer have been scanned. The 3D model has sub-millimetre accuracy, and can be used to study and measure their physical aspects without the need to touch the original.

3D laser scanning has also been used to record graffiti on a tree trunk on Salisbury plain on which the names of soldiers stationed there during training for both World Wars. Since they were carved the tree has grown, the bark expanded and the names have become harder to read. This visualisation shows how 3D data may be able to enhance the carvings and read the names more clearly, preserving them for the future. It may be possible to correlate the information on some of the trees with military records including dates of deployment on Salisbury Plain and the fate of the soldiers who carved their names.

We are very grateful to the Environment Agency for permission to use the LiDAR dataset from Stonehenge, and to Gareth Beale and Graeme Earl from the Archaeological Computing Research Group at the University of Southampton for processing the tree graffiti data during a hectic run-up to a season of excavations in Italy.

Find out more about our 3D laser scanning services.

Share our web content

Eagle-eyed readers of our website might have noticed a new addition underneath the last paragraph of most pages.  It is a little link saying "Share This". Clicking the link allows you to email the page to a friend, or add it to your favourite social networking website such as Facebook, MySpace, Delicious and StumbleUpon.

If you haven't seen what it looks like, here is a screenshot of the window that appears after link after it has been clicked:

Share ThisShare This

If you are logged in to Facebook, for example, clicking the Facebook logo opens up a new window (or tab) in your web browser where you can describe the link and post it to your profile. 


If you want to blog about anything on our website, the Share This link helps to make this a bit easier. Just click the "Post" tab and click the logo of the service that you use to blog (or micro-blog). The usual services are there, such as Blogger, WordPress, Twitter, LiveJournal, etc. Clicking your service will either open a new window, or ask you to log in, and you'll be posting the page details to your blog in seconds. No details are held on our servers!

Sharing pages by email

If you just want to tell a friend about one of our pages by a more 'traditional' method, then you can click the "Send/Email" tab on the ShareThis window, and fill out your details and those of the person you want to send the page link to.

I hope that this little feature comes in handy!

Website News: Home and Explore

Wessex Archaeology hompage, July 2008Wessex Archaeology hompage, July 2008Regular visitors to our website will have noticed a few changes during the past fortnight. Now that we have completed the transition of our website to a content management system, I have had a chance to focus on useability and navigation.


The first change is a complete redesign of the homepage. I have wanted to design something bright, bold, and easy to use for some time now, and, thanks to Drupal, I have been able to do just that. It represents a departure from our past homepages, in that there are fewer words describing services and capabilities, and more focus on content and finding things.

Who Wessex Archaeology are, and what we do, is now covered by one sentence, in a large font, at the top of the page, with an inviting link to our "About" page (also soon to be updated). The 'latest news' block now aggregates the titles of latest posts from across all of our blogs, and we can now include a nice, bold, featured photo at the top of the page, with a large search box underneath it. Tag clouds provide a fun way of browsing the site, and we also list our growing number of blogs.

The large blue box contains a quote from Sue Davies, our CEO, explaining what archaeology is, and what it can do for us. It is good to define archaeology, and the context within it that we work, on the front page.


I have long thought that the word "Projects" was perhaps not the best way to describe our work. From talking to people, and doing some useability testing, it became apparent that I was right. From our homepage, more people were reaching for the search link than the projects link.

The old projects page simply contained a list of periods, counties, and Coastal and Marine projects.While this was very easy to use, there was no space left to include related content that was not directly linked to a project. Thus the Explore section was born.

Explore was going to be a sub-section of the projects page, but given the problems with the word 'Projects' in our main navigation bar at the top, I decided to change things completely.

Our new Explore section contains prominent, brightly coloured blocks of information about the different aspects of our work. At the top are links to projects by period, place and tag, so that it is still very simple to jump into our work via a 'traditional' route (although tags are a bit new...). The period and places pages contain new Google maps to help make finding projects a little easier. New themes and reports sections, and a syndicated news (more on them later) section are linked from Explore, all with colourful icons from the kNeu! icon set.

The Explore section will change and grow to reflect all aspects of our work, in ways that we have never done before.

I hope that our website is now a little easier to use, and certainly a bit more colourful. We hope you like it. If you have any suggestions, please feel free to leave a comment.

New Photo Gallery

As detailed in my previous post about our recent server problems, we had to disable our archaeology photo gallery earlier today. I have spent most of the day putting together a new version that would be independent of our "workhorse" content management systems, WordPress and Drupal. If we experience very heavy workloads then we can easily detach the gallery and move it to a different server, without having to move other parts of our infrastructure.

The new Wessex Archaeology photo galleryThe new Wessex Archaeology photo galleryThe new gallery, while more or less identical in terms of functionality to its predecessor, also gave me the opportunity to give it a new look. I have opted for a dark theme on a black background to bring the focus on to the photographs themselves. It is based upon the Satellite Flickr gallery script by Ted Forbes, and thanks to his excellent and clean templates, I was able to rapidly customise and style the gallery into our own theme.

The eagle-eyed amongst you will also note that the URL of the gallery has changed from to - a 301 redirect has been set up to let search engines know that it has moved, and to keep people's bookmarks working for the time being.

Feel free to leave any feedback about the new gallery here. Happy browsing!

Server problems

[Update] The photo gallery is now online again. Fingers crossed this version will last!

Visitors to our website over the past few days will have noticed that all of our websites were either very slow or even unreachable. Some of you may have seen an triumphant error message stating that there had been a database connection error. Well, our poor server has become rather overloaded - one of the consequences of being a popular desitination on the web for all things archaeological..!

A closer look at the load on our server pointed towards the scripts that run our photo gallery. Unfortunately, the database that the scripts connect to had become corrupted, and the tables had inflated to a rather large 2GB, and MySQL (the database engine that runs our websites) began to consume a lot of RAM (memory). In fact, all physical memory on the server was being used, as well as nearly 2GB of swap (virtual memory). This caused the whole server to essentially grind to a halt. For the server-literate folks out there, our server load average peaked at 9302%...

For the time being, I have had to temporarily close our photo gallery while I try and fix it. Since this is one of the most popular sections of our website, I am hoping to return to normal service as soon as I can. I will post here when normal service resumes.


Comments and CAPTCHAs

A blog isn't much of a blog unless it is possible to leave a comment, to enable conversation and debate. While we simply do not have the time to enable (and crucially, moderate) comments on all of our content, you can now leave a comment on all of our blog entries.

It has taken a little while to get comments set up on Drupal in a secure manner, and quite a few lessons were learned along the way. I don't want you all to have to set up an account just to leave a comment - I know I hate doing that myself. It should be simple and quick to leave a comment, and, hopefully, now it is. Click the "Add a new comment" link below to leave one.


While we all get junk (spam) email, those of us who run websites know that spammers don't just stop at email. Any website that accepts comments is also a target for comments containing links to unsavoury websites, dubious pharmaceutical deals etc. To check that you are a human genuinely wishing to leave a comment, as opposed to a computer program trying to leave rubbish, I have installed a CAPTCHA.


All you have to do is type the two words as you see them, as shown in the above image. If the words aren't clear enough, click the little 'cycle' button next to the box. This will hopefully load in a better image. Then, if you get the words correct, your comment will fly through the internet and into our comments inbox, where we'll check it's OK and publish it below the blog post.

The reCAPTCHA scheme also has a hidden agenda. Many of the world's libaries are digitising their collections of printed material. Optical character recognition (OCR) software "reads" the content and converts it into computer recognisable text (like a word processor document). The trouble is, computers aren't (yet) as good as humans at reading, and sometimes they get it wrong, or simply can't read a word at all. This could be because the ink has bled on contact with the paper, or because the type was pressed too hard, etc. The reCAPTCHA system takes the words that computers can't read, and passes them on to humans to decipher. So by leaving a comment you are helping to digitally preserve a book as part of a scheme set up by Carnegie Mellon University in the USA.

Read more about the reCAPTCHA scheme on Wikipedia.

Follow our news with Twitter

Wessex Archaeology on TwitterWessex Archaeology on TwitterTwitter, the social 'micro-blogging' service that allows users to post short, 140 character updates (or "tweets"), has been very popular amongst members of our IT department. It allows users to 'follow' each other to stay up to date with what they are up to. Updates from your friends can be delivered via the Twitter website, instant messaging, SMS, or via desktop software. It tends to be a very rapid form of communication, with most people seeing updates within minutes of them being published.

I have set up a Twitter account for Wessex Archaeology.  All of our blogs are configured to send a quick 'tweet' whenever new content is posted, so that followers of WA on Twitter can be alerted of new announcements within minutes.

For those who wish to learn more about Twitter, Wikipedia has an excellent article about the service, or of course, head over to Twitter and sign up for a free account to explore it for yourself.


Our Website

Screenshot of the Wessex Archaeology website in May 2002Screenshot of the Wessex Archaeology website in May 2002A lot has happened on the Wessex Archaeology website since I began looking after it in early May 2002. Before then we had a small brochure-style site listing our services, created using an ageing copy of Serif Page Plus by our Drawing Office. Thanks to the Internet Archive, a copy of our website from those days can still be seen (minus the graphics). We were not publishing any archaeological information online at the time.

Keen to improve it, I was tasked with creating a new version of the website using Dreamweaver. This was just in time to coincide with a major discovery made by Wessex Archaeology staff: The Amesbury Archer. Interest in the story of the Archer was huge, and I was able to use our website to help distribute as much information as we had to satisfy global demand for copies of the press release and print-ready photographs. Newspapers and TV stations linked to our website, and very quickly our website went from being under the search engine radar, to being very much in the limelight.

Since May 2002, the website has steadily grown, and we have tried to be innovative in our approach to web publishing. We were one of the first archaeological organisations to start a blog in December 2004. We started podcasting and using Flickr in 2005, began posting videos to YouTube in 2006, and posting selected reports and other documents to Scribd in 2007.

The use of social media websites like these allows us to reach out to new audiences.  Our aim is to help people learn about their past through archaeology, and to make it as easy as possible for the information that we are able to put online to be found. 

In June this year (2008) we migrated our website into Drupal, an open source content management system. This introduced many new features to help us communicate our archaeological work more effectively.

The Website Blog will keep visitors to our site up-to-date with the latest features and content, and in the spirit of open source software, share some of our experiences too. Comments will be enabled when I have time to set up and test the user roles. Comments are now open!

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